The invention relates to a test method for a method for passively obtaining target data about a moving target which is emitting wave energy, in particular sound, by means of which direction angles are measured as actual target data at successive track positions of a vehicle, in particular of a water vehicle, which determines its track positions using an on-board autonomous navigation system, in particular an integrated navigation system, by finding the direction of the target by means of an on-board-based direction-finding system, with the target range, the target velocity, the target course and/or the target position being determined from this as further actual target data.
In order to determine the position, the velocity and the course of a target, for example of a surface vessel, of a submarine or of a torpedo, as so-called target data from a vehicle, for example a submarine or a surface vessel, without revealing itself, in the case of a method which is known as a TMA (target motion analysis) method for passive target data determination (DE 101 29 726 A1) sound which is emitted from the target is received by a sonar direction-finding system, and the direction angle to the target is measured. Starting from an initial position, a position of the target is estimated from this direction angle together with the track position of the vehicle or the vehicle's own position, with this position being that which the target which is moving at an estimated target velocity will assume after a time interval, and an associated estimated direction angle is calculated. The difference between the measured direction angle and the estimated direction angle is reduced iteratively until an error limit is undershot, that is to say, the estimated direction angle corresponds to the measured direction angle, except for the error tolerance. The basic estimated position is identified as the target position. The estimated range to the target, the target velocity and the target course are calculated from the direction angle and the target position. The vehicle's own positions and track positions are determined in a known manner by means of an on-board autonomous navigation system, normally by means of an integrated navigation system, by means of which the direction of travel and the distance traveled are determined by measuring the velocity of the vehicle. The velocity is determined by a Doppler log, for which wave energy is transmitted directionally and is received, Doppler-shifted, after reflection on the ground or on layers in the transmission medium. The Doppler shift is a measure of the velocity. Doppler logs on water vehicles transmit sound waves which are reflected from the seabed, in the case of the “bottom track”, and from water layers, in the case of the “water track”. In the case of the “water track”, the integrated navigation uses the flow in the measurement region to produce dependent track positions which are subject to flow and are corrected by flow data from flow atlases, in order to determine the vehicle's own true position from the measured track position.
A so-called SAT (sea acceptance test) is carried out in order to verify the validity of a TMA method such as this, in which the directions of one or more targets from the vehicle are found using one or more sensors in a sonar direction-finding system. When using the TMA method, target ranges and target velocity, target course and target position are estimated as target data from the north-related direction angles obtained from the directions that are found, which target data must reach specific error tolerances for validation after a specific run-in time.
The invention is based on the object of specifying a test method which can be used with an SAT and by means of which the acceptability of a method for passively determining target data can be determined quickly and preferably on-line.